Well, a lot of style guides prefer "front end" and "back end" instead of one word (similarly to a web server, and not a "webserver"). If that's given, "micro"

Well, a lot of style guides prefer "front end" and "back end" instead of one word (similarly to a web server, and not a "webserver"). If that's given, "micro" creates a compound noun that comes with a dash. Hence, micro-front end. Whether it's correct, that, I strongly suspect, depends more on your style guide than anything else. As far as I'm concerned, whatever makes the technical writer happy is good for me...